Golf ball manufacturers have been experimenting with various materials and manufacturing methods for golf balls over the years in an attempt to improve overall performance and durability and to further refine the manufacturing process.
Golf ball manufacturers have also attempted to address durability and performance issues by manipulating the materials used to form the core and cover layers of golf balls. For example, manufacturers use ionomer resins to form golf ball covers because of the durability, rebound, and scuff resistance characteristics of the materials. However, while ionomer resins are more durable than other types of golf ball layer materials, the same properties that result in durability also provide a hard “feel” and generally result in a lower spin rate and, thus, lower control, due to the hardness of the material.
Alternatively, polyurethane compositions produce “soft” covers and typically allow for greater control because of the increased spin. Because conventional polyurethane cover materials are typically formed of aromatic components, the ultraviolet degradation of the material, which leads to yellowing, led to the recent trend toward light stable cover materials, such as aliphatic polyurethane and polyurea materials. Whether aromatic or aliphatic in nature, however, the relative softness of the polyurethane and polyurea materials, as compared to, for example, ionomer resins, introduces durability issues. In addition, when the inner cover layer of a golf ball is formed from an ionomer resin and the outer cover layer is formed from polyurethane or polyurea, adhesion between the layers is a concern. In an effort to remedy potential delamination of the layers, the inner components of most commercially available polyurethane- or polyurea-covered golf balls are surface treated, e.g., corona discharge/silane dipping, to overcome the adhesion problems. The surface treatment, however, adds cost and time to the manufacturing process.
Further attempts to compensate for the “hard” feel of ionomer-covered golf balls and durability and adhesion issues with polyurethane-covered and polyurea-covered golf balls have resulted in blends of hard ionomer resins, i.e., resins with hardness values of about 60 Shore D and above, with relatively softer polymeric materials. For example, blends of hard ionomers with polyurethanes have been used to form intermediate layers and cover layers of golf balls. However, such blends generally have processing difficulties associated with their use in the production of golf balls due to the incompatibility of the components. In addition, golf balls produced from these incompatible mixtures will have inferior golf ball properties such as poor durability, cut resistance, and the like.
There are many similar examples of materials that have beneficial qualities to golf ball manufacturers, but, because of certain detrimental qualities, cannot be used independently of other more conventional materials. For example, a material with poor moisture resistance, poor durability, or low resiliency would not be useful on its own to form a layer of a golf ball. These types of materials are generally blended with other materials or not used at all.
Additionally, water absorption represents a major hurdle for golf ball manufacturers seeking to increase golf ball durability without affecting golf ball performance. The characteristics of a golf ball can change significantly during a short period of time if the ball absorbs moisture. Such moisture absorption may affect the weight of the ball, as well as the physical and mechanical characteristics of the various materials that make up the different pieces of the golf ball structure, including the cover, the core and the mantle.
While certain polyols or polyamines provide more stability to a polyurethane or polyurea material in terms of moisture resistance, polyurethanes remain highly susceptible to changes in their physical properties due to absorption of moisture. To avoid moisture absorption, manufacturers have attempted to use moisture barrier layers, e.g., U.S. Pat. No. 5,820,488, located between the core and the cover. U.S. Pat. No. 7,306,528 discloses a thin film forming a moisture vapor barrier between the core and the cover of the golf ball with a moisture vapor transmission rate preferably lower than that of the cover to decrease the amount of moisture penetrating into the core of the golf ball.
However, there still remains a need for materials that are resistant to absorption of moisture suitable for forming a golf ball component in a way that capitalizes on the beneficial nature of the material while at the same time minimizing or completely overcoming the detrimental qualities. For example, it would be advantageous to form a golf ball layer or coating from a composition that incorporates modified organic clays or the like to take advantage of the beneficial properties of the clay that exhibit increased water resistance and better performance characteristics, greater exfoliation, and enhanced mechanical strength than conventional nanoclay compositions. In addition, golf balls having structural and/or coating layers formed, at least in part, from such compositions would be advantageous.